The power with which a cellular telephone, also referenced to as a mobile phone, transmits messages regulated by commands from the cellular base station, also referred as a base-transceiver station (BTS), which sets it to a specified level. Regulation occurs to prevent cellular phones near a tower from generating a signal so strong as to interfere with BTS reception from other units located further from the tower. Ideally, all phones will transmit at levels which appear equal at the tower. The transmit power levels are also managed to minimize interference with surrounding cells. This management is well-known in the art, and is described, e.g., in the US Standard for CDMA, TIA/EIA-95B, March 1999, pages 6-5 through 6-12.
Modern mobile phones are designed for power-conservation. They are typically constructed from CMOS circuits which consume significant power only when switching. The processor and many ancillary features are designed with an operational state and one or more low-power “sleep” states where switching rates are reduced or terminated for power conservation. Such phones “wake” periodically to receive and respond to polls from the BTS and to inputs from the user.
Referring to FIG. 1, for illustrative purposes a conventional mobile phone is shown.
FIG. 2 shows two conventional mobile phones (201, 202) at differing ranges from BTS 200. The signal 204 transmitted from mobile phone 202 is transmitted with greater power than signal 203 transmitted from mobile phone 201 located in close proximity to BTS 200. Clearly, the battery of mobile phone 202 will discharge more rapidly than that of mobile phone 201.
FIG. 3 depicts a problem addressed by the present invention. Mobile phone 100 is unable to communicate with BTS 200 due to the influence of shielding 300. BTS signals 301 cannot reach mobile phone 100. The signal 302 of mobile phone 100 does not reach BTS 200 although the mobile phone 100 is transmitting at maximum power while rapidly discharging its battery.
FIG. 4 is a flowchart illustrating the operation of conventional mobile phones. When in an open-loop mode, i.e., prior to achieving two-way communication with the BTS, the mobile phone starts probing 401 in the open-loop mode with an estimated power level based on the power level received from the base station. If a response 402 is not received and the mobile phone is not transmitting at maximum power 403, power is incremented 404, and a subsequent probe 405 is transmitted. This process is repeated until a response is received 402, or when maximum power 403 is reached. If maximum power is reached without receiving a response, the mobile phone continues sending probes at maximum power 405. If a response is received, the mobile phone enters a closed-loop mode 406, and transmits at power levels commanded by the BTS 407, as long as contact with BTS is maintained. If the contact with BTS is lost, the mobile phone re-enters the open-loop mode 401.
A variety of sensors may be used, singly or in combination to determine a change in the location of a mobile phone. These include but are not limited to accelerometers, inclinometers, magnetometers, and global positioning systems, all of which sense change in location. Sensors can also detect the presence or absence of local- or personal-area networks, such as IEEE 802.11, defined as a set of standards for implementing wireless local area network (WLAN) computer communication, or Bluetooth (standardized by the Bluetooth Special Interest Group) defined as wireless technology standard for exchanging data over short distances. Generally, a change in reachability to a local network implies a change of location.
The problem addressed by the present invention revolves around a rapid battery drain which occurs when a mobile phone is unable to establish contact with the BTS because it is located too remotely or within a no-reception area such as a shielded building, automotive glove compartment, or steel desk drawer. Users find it extremely frustrating to frequently charge a mobile phone that is not even usable inside an office building, or to take the mobile phone from its storage location in a glove compartment or desk and find it discharged.
Power conservation is an important consideration for mobile phones. The package of every mobile phone carries a rating for battery life in conversation (“talk time”) and passive uses.
In a paper entitled “An Analysis of Power Consumption in a Smartphone,” Carroll, Aaron and Gernot Heiser, 2010 Usenix Annual Technical Conference it is demonstrated that the greatest consumer of power in a smart mobile phone is the Global System Mobile (GSM), a cellphone standard function. Hence reducing or eliminating this power drain when it is non-productive is the best way to extend the battery charge lifetime.
Presently, the art addresses power management in a device containing electronics modules for a mobile phone, a wireless personal area network, a wireless local area network, and a pager or short message service. The modules may be selectively powered off to extend the battery life. Yet, the present art fails to address reducing the power expended on mobile phone service without regard to other services.
Although the industry is aware of the desirability of robust power conservation, no solution has been developed which deterministically addresses the technique of quiescing (napping) based on the absence of a signal received.
Accordingly, there is a long-felt need for a reliable, deterministic way to determine when to quiesce the mobile phone, and more importantly, when to restore it to normal operation. This problem has not been addressed in the industry, and neither have approaches to power conservation been considered by determining and using information related to the phone's location.